that's likely not true. Every time you do this: if err := fn(); err != nil { } /...

that's likely not true. Every time you do this:

    if err := fn(); err != nil {
    }
    // the result of fn does not affect the identifier err
    // in the enclosing scope

you're scoping err just to that if block. that's ... just about the most common phrase in all of Go. it won't affect any err defined prior and it won't exist outside of the if block.

You'd have to do this to make the value stick around or affect the enclosing block:

    var err error
    if err = fn(); err != nil {
    }
    // err has the result of fn here